Dementia is easily one of the cruelest disorders to exist.
one of my best friend's dad had it. that man was working constantly throughout his life, building shit left and right: buildings, car shops, airports (yup), airplanes (yup), renovating spaceships for the national museum, etc. the definition of a workaholic, engineer meets handyman, he could do it all. then after the diagnosis he realized he can't do anything without his meds. he drove off the road into a ditch (he never was a bad driver, never had an accident, also used to be a rally racing driver), he couldn't fly anymore obviously, he couldn't help his son while renovating their house, etc. he slowly but steadily started to become a mess. he hang himself before he became completely helpless and a 100% pain in the ass for the family.
i'd do the same honestly.